Bait the Dog: Nellie does this first to Anna, when she's forced to apologize to her, by pretending to show genuine remorse and complimenting on her advance in her speech, luring Anna into thinking she wants to make amends and be her friend, and then when she tells Laura she'll allow Anna into their club, only to use the initiation as an opportunity to humiliate her.
Blackmail: Nellie finds out that Laura stole the music box and uses it to blackmail her into participating in a scheme to bully and humiliate her friend with a stutter.
Bullying the Disabled: Nellie keeps mocking Anna Gillberg's stutter at every opportunity.
Catapult Nightmare: Laura's guilt-induced nightmares cause her to wake up in the middle of the night gasping and sweaty, much to Mary's annoyance, who doesn't know the real reason why her sister is acting so strange.
Don't Make Me Take My Belt Off!: Nels tries to spank Nellie after catching her mocking Anna's stutter, and only declines under Harriet's protests and the condition that Nellie go apologize to Anna and her family. When he's told Nellie used Laura's music box stealing to blackmail her into helping her humiliate Anna, he sends her to her room instead of going to the school, telling her that she'd learn "a different lesson" and then goes up with his belt.
Immigrant Parents: Anna's parents are immigrants from Sweden. When Nellie is forced to go visit her and apologize, she's relieved from having to face her parents' anger thanks to them not understanding her language.
Easily Forgiven: After being humiliated during the club initiation and thinking Laura played a part in the scheme (which Laura was partially to blame for), Anna forgives Laura rather quickly after being promised she'll dedicate all of her free hours to work on Anna's speech.
Kids Are Cruel: During Anna's initiation to the club which Nellie uses to force her to read "The Peter Principle" and humiliate her, all the other girls can be seen giggling and laughing at her.
Nice Job Fixing It, Villain: Nellie blackmailing Laura, ironically, may have saved the latter from punishment. Had she merely reported Laura from stealing the music box, Nels would have no choice but to agree that she should be serverely penalized when Charles decided the punishment was up to him. But because she chose to blackmail Laura and then forced her to distance herself from Anna and be complicit in her schemes, Nels decided Laura had suffered enough and focused only on Nellie's faults.
Nightmare Fuel: In-universe. Laura's guilt over having stolen the music box causes her to have terrible nightmares in which she's sentenced to write for all eternity at school, and another where she's executed at the gallows (and Nellie is the executioner!).
Ordered Apology: After catching Nellie mocking Anna's suttering, Nels tries to spank her but relents and demands that she apologize to the girl when his wife talks him out of using the belt.
Villain Ball: In the end, using her club to humiliate Anna is the final straw for Laura, who after making amends with Anna, decides to confess her stealing and expose Nellie's blackmail. Had Nellie not gone out of her way to hurt Anna, Laura might not have confessed right away.
